The morphology controlled molecular assemblies play vital roles in biological systems. Here we present endogenous reactive oxygen species (ROS)triggered morphology transformation of polymer−peptide conjugates (PPCs) for cooperative interaction with mitochondria, exhibiting high tumor therapeutic efficacy. The PPCs are composed of (i) a β-sheet-forming peptide KLVFF conjugated with poly(ethylene glycol) through ROS-cleavable thioketal, (ii) a mitochondria-targeting cytotoxic peptide KLAK, and (iii) a poly(vinyl alcohol) backbone. The self-assembled PPCs nanoparticles can enter cells and target mitochondria. Because of overgenerated ROS around mitochondria in most cancer cells, the thioketal linker can be cleaved, leading to transformation from nanoparticles to fibrous nanostructures. As a result, the locational nanofibers with exposure of KLAK exhibit enhanced multivalent cooperative interactions with mitochondria, which causes selective cytotoxicity against cancer cells and powerful tumor suppression efficacy in vivo. As the first example of ROStriggered intracellular transformation, the locational assembly strategy in vivo may provide a new insight for disease diagnosis and therapy through enhanced interaction with targeting site.

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The shape of a drug delivery system impacts its in vivo behavior such as circulation time, accumulation, and penetration. Considering the advantages of functional dyes in bioapplications, we synthesize a class of nanoaggregates based on BF 2 -azadipyrromethene (aza-BODIPY) dyes, which can realize long blood circulation and deep tumor penetration simultaneously in vivo through morphological transformation modulated by a nearinfrared (NIR) laser. First, when the temperature increases, the wormlike nanofibers of the aza-BODIPY-1 aggregate, possessing a long blood circulation time, can be transformed into spherical nanoparticles, which are conducive to increasing the penetration in the solid tumor. Second, without any postmodification, the nanofibers exhibit an outstandingly narrow absorption band in the NIR spectral range, so that they possess ideal photothermal properties. Through 655 nm laser irradiation, the intrinsic photothermal effect causes a local temperature increase to ∼48 °C, realizing the transformation of 1-NFs to 1-NPs. Third, the morphological transformation is real-time detected by photoacoustic (PA) imaging. By monitoring the change of the PA signal at a specific wavelength, the in vivo deformation process of nanomaterials can be traced. Consequently, the in situ morphology transformation of aza-BODIPY-based nanomaterials can simultaneously realize long blood circulation and deep penetration, resulting in the enhanced antitumor outcome.